Packed‐Column of Granular Activated Carbons for Removal of Chemical Oxygen Demand from Industrial Wastewater     

Sawanya Laohaprapanon  Marcia Marques  Fabio Kaczala  William Hogland 《洁净——土壤、空气、水》2013,41(3):244-250

In the present study, chemical oxygen demand (COD) removal by packed‐columns of activated carbon (AC) derived from two different materials (coal activated carbon, CAC and wood activated carbon, WAC) is reported as part of an on‐site wastewater treatment system for handling small volumes of wastewater generated at wood‐floor industries for which there are no proper on‐site treatment options available in the market. The performance of the sorbents, the effect of bed depth (0.19 and 0.57 m) and volumetric load (0.10 and 0.24 m h^?1) on the breakthrough curve of sorption systems were studied. The results indicated the feasibility of using both ACs to treat these wastewaters. At the bed depth (0.57 m), volumetric load (0.24 m h^?1), and 30% breakthrough, CAC and WAC showed treatment capacity of 40.5 L kg^?1 in 250 h and 23.8 L kg^?1 in 63 h, respectively. This indicated that CAC requires longer retention times to reach a performance similar to WAC. The experimental data was fit into the bed depth‐service time model showing that under the same conditions, CAC had higher maximum sorption capacity (N₀) than WAC. Moreover, thermal regeneration at 500°C temperature could be a cost‐effective procedure since the reuse of spent AC through such regeneration process for further treatment could still achieve 90% of the initial sorption capacity, reducing then costs for the use of new sorbents and also the need for waste disposal.  相似文献   

Climatic Controls of Saguaro (Carnegiea Gigantea) Regeneration: A Potential Link With El Niño     

《自然地理学》2013,34(6):465-475

Saguaro cacti establish periodically in cohorts during years that are climatically favorable. Determining the establishment year is complicated by age-height relationships that vary considerably from site to site and require extensive data collection. Estimations of age-height relationships for only a few locales have thus limited the ability of researchers to estimate age in other populations, and consequently to relate periods of regeneration to climate. We collected data for 254 saguaros in the arid western portion of the species' range and employed a recently developed site-specific technique for estimating saguaro age to reconstruct the population structure at this locale. Second, we used discriminant analysis to determine which climate variables best predict regeneration years. We found that above-average temperatures in November coupled with concurrent high soil moisture levels, conditions typically associated with El Niño years, are associated with years characterized by high regeneration. Accordingly, these results suggest that El Niño events may be related to years of favorable regeneration for saguaros.  相似文献   

Saguaro (Carnegiea Gigantea) Densities and Reproduction Over the Northern Sonoran Desert     

《自然地理学》2013,34(6):505-518

Casual observations suggest that saguaro populations are densest in southeastern Arizona, although data have not been collected and no study has been done to address this topic. In addition, the topic of reproductive density has similarly never been addressed. Saguaro reproductive output is directly related to the number of adult individuals and the number of branches in the area. Thirty saguaro populations over their U.S. range were sampled to consider two variables: population density and reproductive stem density. Stepwise regression using climate and vegetation (e.g., availability of nurse plants) to predict density yielded tree + Ambrosia cover and maximum July precipitation. Nurse cover, however, is also influenced by summer rain. The partial correlation results suggest that high saguaro densities are linked with high quality nurse cover (i.e., not Larrea tridentata) in addition to summer rainfall. Total cover and mean annual precipitation are the best predictors of reproductive stem density. Mean annual precipitation may be a good predictor of reproductive stem density, because population density is linked with summer rain while branching is linked with winter rain. The plots were also divided into climatic regions. One-way ANOVA shows that the northeast (high winter precipitation) and west (dry) have lower saguaro densities than the southeast (high summer precipitation), while the northeast and southeast both have very high reproductive stem densities relative to the west. The warmer west is less susceptible to periodic freezing mortality, while previous work has shown that the southeast generally regenerates more successfully. Thus in the colder northeast, which is also outside of the primary summer rain and best nurse plant belt, low density populations seem to be maintained only with high reproductive density.  相似文献   

An experimental study on the relationship between acoustic parameters and mechanical properties of frozen silty clay   总被引：1，自引：0，他引：1  

Xing Huang  DongQing Li  Feng Ming  JianHong Fang 《寒旱区科学》2013,5(5):0596-0602

To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5(T) nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of 1 °C to 5 °C. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ultrasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or compressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.  相似文献   

Tree Planting:How Fast Can It Accelerate Post-fire Forest Restoration?——A Case Study in Northern Da Hinggan Mountains,China     

LI Xiuzhen  HE Hong S  WANG Xugao  XIE Fuju  HU Yuanman  LI Yuehui 《中国地理科学(英文版)》2010,20(6):481-490

In 1987,a catastrophic fire burned over 1330000 ha in the densely forested area of the Da Hinggan Mountains in the northeastern China.After the fire,intensive management including burned trunk harvesting and coniferous tree planting had been conducted to accelerate forest restoration.To study the long term effect of these activities on forest recovery,we used a simulation modeling approach to study long-term(300 years) forest dynamics under current planting and natural regeneration scenarios.Results indicat...  相似文献   

Disturbance,geomorphic processes and recovery of wildfire slopes in North Tyrol     

Oliver Sass  Michael Heel  Karl‐Friedrich Wetzel  Arne Friedmann 《地球表面变化过程与地形》2012,37(8):883-894

Wildfires in the sub‐alpine belt of the Austrian Limestone Alps sometimes cause severe vegetation and soil destruction with increased danger of secondary natural hazards such as avalanches and debris flows. Some of the affected areas remain degraded to rocky slopes even decades after the fire, raising the question as to whether the ecosystems will ever be able to recover. The mean fire interval, the duration of recovery and the role of geomorphic processes for vegetation regeneration are so far unknown. These questions were tackled in a broad research approach including investigation of historical archives to determine the frequency of historical wildfires, mapping vegetation regeneration on 20 slopes of different post‐fire ages, and soil erosion measurements on two slopes. To date, > 450 historical wildfires have been located in the study area. The mean fire interval per square kilometre is c. 750 years, but can be as low as 200–500 years on south‐facing slopes. Vegetation regeneration takes an extremely long time under unfavourable conditions; the typical window of disturbance is between 50 and 500 years, which is far longer than in any other wildfire study known to us. Soil erosion constantly increases in the years after the fires and the elevated intensity can be maintained for decades. A two‐part vegetation regeneration model is proposed depending upon the degree of soil loss. In the case of moderate soil erosion, spreading grassland communities can slow down shrub re‐colonization. In contrast, after severe soil destruction the slopes may remain degraded for a century or longer, before rather rapid regeneration occurs. The reasons are not fully understood but are probably governed by geomorphic process intensity. The interdependence of vegetation regeneration and geomorphic processes is a paradigm of ecology–geomorphology interaction, and is a unique example of a very long‐lasting disturbance response caused by wildfire in a non‐resilient ecosystem. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Ecological influence of exotic plants of Sonneratia apetala on understory macrofauna     

TANG Yijie  FANG Zhanqiang  CHEN Kang  ZHANG Zaiwang  ZHONG Yanting  AN Dong  YANG Xiongbang  LIAO Baowen 《海洋学报(英文版)》2012,31(5):115-125

The study aims to compare the differences of macrofauna communities of wetlands at 3-year-forest- age, 5-year-forest-age Sonneratia apetala artificial mangroves, 5-year-forest-age Kandelia candel ar- tificial mangroves with the same restoration background, and the naked tidal flat in the Qi’ao Island Mangrove Nature Reserve of Zhuhai, Guangdong Province. The results show that there were signif- icant structural differences in macrofauna communities among four kinds of habitats. The increase of biomass and species diversity of macrofauna at 3-year-forest-age S. apetala artificial mangroves was obviously faster than that at 5-year-forest-age K. candel artificial mangroves whose average tree height was close to that of 3-year-forest-age S. apetala artificial mangroves. The BIOENV analysis shows that it was related to the rapid growth of S. apetala, which rapidly changed the light level and shading conditions in the forests. The 5-year-forest-age S. apetala artificial mangroves had lower macrofauna species diversity but higher density and biomass than K. candel artificial mangroves with the same forest age. This was due to the rapid changes of physical and chemical properties of habitat soil by the ecological restoration of S. apetala artificial mangroves as well as the changed food sources possibly caused by the leaf-litter of such non-indigenous mangrove species S. apetala. However, further survey should be conducted on whether there are any negative ecological impacts of large-scale cultivation of S. apetala on macrofauna communities, so as to evaluate correctly S. apetala’s role in the restoration of coastal mangrove ecosystems.  相似文献   

微拟球藻原生质体制备与再生     

马晓磊  张琳  杨官品  朱葆华  潘克厚 《海洋科学》2012,36(2):19-23

综合考虑酶混合液处理时间和初始细胞密度两个因素,选取终浓度为4%半纤维素酶和2%崩溃酶的酶混合液对一株海洋经济微藻——微拟球藻(Nannochloropsis oculata)进行原生质体的制备与再生,Calcofluor White染料染色可在荧光显微镜下观察到完整的原生质体细胞。实验结果表明:同一初始密度藻细胞酶处理1～3 h制备率较高;酶处理相同时间较高初始密度(2×107～3×107cells/mL)的藻细胞制备率较高,并且原生质体在再生培养基上可再生,生长趋势与野生型细胞一致。考虑到酶处理时间过长或者密度过大会对原生质体的再生产生影响,本实验选择最适酶处理时间为1h,初始细胞密度为2×107cells/mL。  相似文献   

Land use/cover, landforms and fragmentation patterns in a tropical dry forest in the southern Pacific region of Mexico   总被引：1，自引：0，他引：1  

Leopoldo Galicia  Alba Esmeralda Zarco-Arista  Karla Ivette Mendoza-Robles  José Luis Palacio-Prieto  Arturo García-Romero 《Singapore journal of tropical geography》2008,29(2):137-154

In spite of widely documented studies of deforestation rates and land use/cover changes in tropical dry forests in Mexico, relatively little is known about fragmentation patterns in such forests. This study defines the spatial distribution of landforms and land use/cover types the lower Papagayo River basin and examines their influence on fragmentation patterns and biological diversity in a tropical dry forest in that southern Pacific region. The land use/cover map was constructed from aerial photographs, Landsat TM imagery (2000) and fieldwork. Landform units were defined based on altitude, slope, lithology and morphology. Landscape fragmentation parameters were obtained using FRAGSTATS (version 3.3) considering the numbers of patches, mean, minimum and maximum patch size, edge density, total edge and connectivity. Results show tropical dry forest to be remnant vegetation (~11 per cent), characterized by isolation and low connectivity. Land use/cover types have different effects on fragmentation patterns. Agriculture and cattle raising produce similar numbers of patches, but with a different mean size; and human settlements have a scattered distribution pattern. The abandonment of rural agricultural livelihoods has favoured the expansion of secondary tropical dry forest characterized by continuity and high connectivity, which suggests a high regeneration potential from land abandonment. It can be concluded that tropical dry forest fragmentation and recovery at regional scales depend on such landscape attributes as lithology, slope, geomorphology and management.  相似文献   

黄海和东海沉积物有机质活性及营养盐再生潜力初探   总被引：9，自引：0，他引：9  

陈建芳  金海燕  刘小涯  李宏亮  林以安  潘建明 《地球化学》2005,34(4):83-90

2000年秋季和 2001年春季,对黄海和东海 6个站位的水柱和沉积物样品进行了营养盐、沉积有机碳、有机碳同位素和氨基酸分析.结果表明, 表层沉积物的有机碳含量和有机质活性存在较明显的季节性变化,这主要由春秋两季表层水体生物量的差异引起.在泥质堆积区 E2、 E4、 E5站,春季表层沉积物有机碳的含量与活性均较高,而同期底部沉积物向上的营养盐梯度也明显增大, 显示有机碳的含量及活性与营养盐再生有密切关系.  相似文献